#define  _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;

class A
{
public:
	int _a = 1;
};

class B : virtual public A
{
public:
	int _b = 2;
};

class C : virtual public A
{
public:
	int _c = 3;
};

class D : public B, public C
{
public:
	int _d = 4;
};

int main()
{
	B b;
	D d;

	return 0;
}